Wet spinning of acrylonitrile polymer fibers



ct. 10, i967 3,346,685

WET SPINNING 'OF ACRYLONITRILE POLYMER FIBERS Filed Aug. 17, 1964 RQ D. CROZIER yETAL Sheets-Sheet l n Q u w w N o Coaga/a//on empera/ufe, 6

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INVENTORS. Roha/c/. Crayer Richard E. HC1/der dames HfHood Ruper B. H r/e BY TTORNEY 0d l0 1967 R. D. cRzlr-:R ETAL 3,345,685

WET SPINNING OF ACRYLONITRILE POLYMER FIBERS Filed Aug. 17, 1964 5 Sheets-Sheet 2 E 4 5 WW d50/ Conenfr'Gf/'On fn @caga/0 f/'On baffi I INVENTORS Rona/d Crojier R/'chor- E. Harder .Jam es H. Hood R41/oer# B. Hur/ey United States Patent 3,346,685 WET SPINNING 0F ACRYLONITRILE POLYMER FIBERS Ronald D. Crozier, Newport News, and Richard E.

Harder, James H. Hood, and Rupert B. Hurley, Williamsburg, Va., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Aug. 17, 1964, Ser. No. 390,034 13 Claims. (Cl. 264-182) The present invention relates to a method for preparing acrylonitrile polymer fibers having improved properties. More particularly, it relates to a method for wet spinning acrylonitrile polymer fibers from an aqueous inorganic saline solution into an aqueous coagulating bath to produce fibers having improved properties, particularly improved dyeability and resistance to fibrillation.

As taught in U.S. 2,140,921, many polymers including acrylonitrile polymers, can be dissolved in and spun from concentrated aqueous solutions of certain Ihighly hydrated metal salts, such as zinc chloride. It has been reported by other investigators that such salt solutions commonly yield poor fibers when wet spun. The product has been described as brittle, opaque and full of voids. As a consequence, much attention has been given the derivation of spinning systems involving organic polyacrylonitriledissolving solvents, but also, considerable effort has been expended in developing workable wet spin-ning systems utilizing aqueous saline solutions.

The use of organic solvents is expensive and results in a fiber having an irregular cross-section, whereas the fibers wet spun from saline solutions are cylindrical. This difference between fibers spun from organic solvents and those spun from aqueous inorganic salts is due to the different behaviors of the two types of solution when brought into contact with a setting medium. Dry spun organic solutions of the polymer merely lose solvent to the evaporative atmosphere, and the fiber-forming rnaterial collapses on itself as the solvent is removed. Wet spun organic solutions of the polymer are converted into fibers by extraction of the organic medium from the spun dope by the action of a non-solvent in the coagulating bath. The material in the coagulating bath which is a nonsolvent for' the polymer must be miscible, however, with the solvent for the polymer. In common practice the coagulant is water, and the polymer solvent is watermiscible. When spun from such organic solutions, the polymer remains hydrophobic. Hence, the freshly coagulated fiber skin acts as a semi-permeable membrane in transferring solvent from the fiber to the bath and allowing essentially no migration of Water into the core of the fiber, even when the bath contains a high concentration of solvent. In consequence, the cores of the wet spun fibers from organic solutions shrink and set due to the removal of solvent therefrom and to the resultant radial collapse of the fiber to a denser condition, forming a liber of irregular cross-section. The effect, then, of both wet and dry spinning of organic solutions of hydrophobic polymers is primarily one of removing solvent until the concentration of the polymer exceeds the capacity of .the remaining solvent to dissolve it. There is no formation of a stretchable gel, and the polymer can only be rendered plastic by heat in order to be stretched significantly. Because the organic solutions behave in this way, the freshly spun fibers cannot be subjected to any significant amount of cold stretching. Consequently, to make fine fibers from organic solutions of the polymer, one needs spinnerets with Very small orifices, and this necessitates high extrusion pressure to move the viscous solutions through the spinnerets.

As an example of some of the endeavors with aqueous saline solutions, it has been disclosed in U.S. Patents 3,346,685 Patented Oct. 10, 1967 2,648,646 and 2,648,647 that it is possible to obtain good fibers of high acrylonitrile polymers by wet spinning aqueous saline solutions thereof in which the saline constitnents are mixed salts, one of which is capable at higher concentrations of dissolving the polymer `and the other of which is incapable of dissolving the polymer at any concentration in water. It is shown in those patents that the minimum concentration of saline constituents in water to dissolve high acrylonitrile polymers is 55 percent.

It has been taught by Cresswell and his co-workers, in U.S. Patents 2,558,730-2,588,735, inclusive, and 2,558,781, that useful fibers of polyacrylonitrile may be wet spun from aqueous saline solutions thereof, provided that the coagulating bath is at a temperature not to exceed -|-l0 C. and provided further that the bath be mainly water, with specific mention being made of water alone, aqueous ethanol (to prevent freezing the bath at temperatures down to 15 C.), 0.24 normal hydrochloric acid, and dilute salt (sodium chloride) solutions. The so-coagulated fiber is described as a swollen or gelled article having marked elasticity and toughness. It can be washed free of salt and hot stretched to make strong fibers. The same patents state that when the saline solutions of the polymer are coagulated at temperatures materially above +10 C., the produ-ct is a non-transparent, weak gel having little or no ductility. Because of the high viscosity of the saline solution of polymer, the solution is supplied under pressure to the spinneret and its mobility is increased by heating it before it passes through the small spinneret orifices into the cold coagulating bath.

Each of the aforementioned patents relative to wet spinning of saline solutions of polyacrylonitrile is an advance over the prior art, yet none of: them teaches a spinning method which is free from certain serious limitations. Thus, as shown by the small orifices required to make fine fibers, and the low temperatures required for coagulation in water and dilute acids, alcohols or salts, it is apparent that low coagulation temperature alone does not assure high rates of production at low extrusion pressures. It has been found, as well, that when fibers are spun from the aforementioned mixed salt brines into such an abrupt coagulant as water, there is obtained a physically non-uniform product. This is due, apparently to the initial formation of a hard sheath about the still fluid core of the freshly spun fiber, and any stretching to effect a reduction in diameter results in rupturing the fiber.

As an improvement over the foregoing patents, it has been reported by Stanton et al. in U.S. 2,790,700 that markedly improved fibers may be spun from aqueous salt solutions of polyacrylonitrile, or of high acrylonitrile linear copolymers, containing a single salt or a mixture of solvent and non-solvent salts, when the saline solution medium is extracted gradually and under controlled conditions in the coagulating bath. According to the method described therein, the saline solution of the polymer is spun first into an aqueous coagulant bath consisting of a solution in water of the same salt or salts as are in the spinning dope, at concentrations controlled within a narrow range but whose absolute values vary with variations in spinning rate, spinneret size, spinning dope concentration, and coagulation temperature. In all cases, the coagulating bath has a concentration of the salt or salts such that the spun fiber can be taken away from the spinneret orifice without breaking, at a linear rate 4 or more times that at which the spinning dope enters the bath from the spinneret. Unless the freshly spun fiber is coagulated under conditions which would permit such a takeaway rate, and for fine fibers, small orifices are required. Further, unless the fibers initially exhibit liquid-like flow, coagulation is non-uniform, and any after treatment gives non-uniform products. In the case of zinc chloride solutions of polyacrylonitrile, to get this effect, the concentration in the coagulating bath must be at least 25 percent and not to exceed about 47 percent by weight, and in all cases the coagulat'ion bath temperature is not to exceed 30 C., and for any specific set of operating conditions the optlmum operative range of concentrations falls within a narrow bracket within the stated range. When the strongly saline solution of the polymer is spun into the appropriate lower concentration of the same salt-system, complete coagulation is not instantly effected and the fibers are not .selfsupporting for a short distance, usually more than 1 lnch, from the spinneret.

While the improved method of U.S. 2,790,700 is well suited for the preparation of acrylonitrile polymer fibers, for some reason, not fully understood, when fibers are spun that are of a copolymer, i.e. of between about 85- 95 weight percent acrylonitrile and the remainder another ethylenically unsaturated monomer or monomers, the resulting copolymer fibers, although of general textile utility, are observed to have poor fibrillation resistance, generally ring dyeing characteristics, low dye yield, i.e., depth of shade or coloration, and poor dye bleed resistance, i.e., after the fiber is dyed, excessive dye bleeds from the fiber on washing, scouring and the like.

We have found, surprising as it may seem in view of the directions of the prior art, that, not only can acrylonitrile copolymer fibers having excellent general fiber properties be prepared by wet spinning in aqueous salt solutions at concentrations and temperatures heretofore thought to produce unacceptable bers, but also, fibers having outstanding fibrillation resistance and dyeability properties are attained. For that matter, we have found that it is essential to spin fibers under these conditions, as hereinafter set forth, in order to produce totally acceptable acrylonitrile copolymer fibers.

The preparation of such copolymer fibers is accomplished in and by practice of the present invention which comprises spinning an aqueous inorganic saline solution of a polymer of -an ethylenically unsaturated monomeric material containing between about 85 and 95 weight percent polymerized acrylonitrile at between about 55 and 100 C. into an aqueous coagulation bath containing, generally, between about 15 and 40 weight percent (which concentrations will be more specifically discussed subsequently herein) of saline or salt constituents, and, preferably, the same saline constituents that are present in the polymer solution, the coagulation bath being maintained at a ternperature between about 20 and abou 50 C.

The invenion will be more fully understood by the ensuing description and specification and the attached drawings wherein:

FIGURE 1 graphically depicts the prior art conditions of wet spinning acrylonitrile polymer fibers;

FIGURE 2 graphically depicts the conditions of the present invention for wet spinning acrylonitrile polymer fibers;

FIGURE 3 graphically depicts, in general relationships, a phenomenon that occurs during wet spinning of acrylonitrile polymer fibers;

FIGURE 4 graphically depicts the indicated phenomenon of FIGURE 3 under given conditions of wet spinning acrylonitrile polymer fibers; and

FIGURE 5 graphically depicts unexpected improvements in dye yield of fibers prepared in accordance with the present invention.

With reference to FIGURE 1, there is graphically illustrated the conditions reported by the prior art for spinning acrylonitrile polymer fibers from aqueous inorganic saline solutions, and illustrated in terms of spinning into an aqueous ZnCl2 coagulation bath, which conditions are reported to be those suited for spinning fibers having acceptable textile fiber properties. The area generally designated M under the curve in FIGURE 1 is, thus, the conditions reported to be useful for fiber manufacture by the Cresswell and coworkers patents referred to hereinbefore; and, the area generally designated N under the curve in FIGURE l is, thus, the conditions reported to be useful for fiber manufacture by the Stanton et al. patent referred to hereinbefore.

FIGURE 2 graphically illustrates the spinning conditions employed in the practice of the present invention for making acrylonitrile copolymer fibers having excellent fiber properties. Such fibers are prepared by spinning an aqueous polyacrylonitrile-dissolving saline solution of the copolymer into an aqueous saline coagulation bath maintained at temperatures and saline or salt concentrations defined by the curve ABCDEF in FIGURE 2. For purposes of comparison, the useful areas reported by the Cresswell and coworkers and Stanton et al. patents of FIGUR-'E 1 are indicated by dotted lines in FIGURE 2 and designated M and N, respectively, in accordance with the terminology used in FIGURE 1. Referring to the area bounded by the curve ABCDEF, it is seen that the ternperature of the coagulation bath employed in the present invention is between about 20 and about 50 C., and the concentration of saline or salt constituent in the coagulation bath ranges from about 15 to about 35 weight percent in the upper region of the area, and ranges from about l5 to about 27 weight percent in the lower region of the defined area ABCDEF.

It will be appreciated by the artisan the significance of being able to prepare fibers following the precepts of the present invention as well as the unexpected results obtained regards the superior properties, and especially dyeability properties, of copolymer fibers prepared following the present teachings. The results obtained by practice of the present invention are especially no-vel in view of the apparent inability, as reported by the prior art, to prepare acceptable fibers under the instant spinning conditions. The reasons for this are not completely understood. One possibility is the finding that, under a given set of conditions, i.e., one polymer, one temperature, one polymer metering rate, etc., when the salt concentration in the coagulation bath is lowered slowly, a concentration is reached, which is reproducible when repeated, at which essentially all of the extruding filaments break off at the face of the spinnerette. The appearance of this inability to prepare filaments is quite dramatic and occurs within a very narrow range of salt concentrations. Then, as the concentration is raised above that minimum concentration level, the coagulation of the fibers appears normal until a concentration of some 1.5 to 2 percent above the minimum is reached at which defects in the coagulated filaments appear and gradually worsen as the concentration is raised to about 3 to 4 percent above the minimum. At this point, although breaking of filaments from the orifice face is not generally observed, it is virtually impossible to prepare filaments of acceptable properties because the coagulated gel filament is so soft and full of defects, and filament bonding is excessive.

The foregoing phenomenon or spinning barrier is graphically illustrated in FIGURE 3. With reference to FIGURE 3, it is seen that as the concentration of salt in the coagulation bath is decreased from right to left along line AB a point is reached at which the spinning cannot be maintained without increasing to a substantial degree the spinning pressure or orifice diameter. This is the point at which, without altering spinning conditions, the filaments break off at the spinnerette face. This is at the point where line A=B connects with line BC. Filament spinning can be maintained after the barrier BC is encountered if the pressure on the spinning solution is increased or if larger diameter orifices are used as by traversing conditions along line BC. Expressed differently, and with reference to FIGURE 3, if other conditions are kept constant and the spinning pressure or orifice diameter are continuously reduced, there is reached a point below which filament formation cannot be maintained. The shaded area of FIGURE 3, then, represents in general fashion, the conditions under which filament formation is not practical.

If the barrier line BC is surmounted spinning can be maintained at lesser pressures or with smaller diameter orifices as represented by the region to the left an-d above the line DEF in FIGURE 3. However, as illustrated, when the barrier is encountered the spinning pressure or orifice diameter must be increased disproportionately for incremental decreases in the salt concentration in the coagulation bath in order to maintain preparation of nonbroken filaments. When the barrier is encountered as discussed, it appears that spinning with lower concentration coagulation baths is not practical in view of the excessive spinning pressures required or large orifices which call for tremendous draw-down of the spun filament in order to make small denier fibers, and fibers prepared with large draw-down in the coagulation bath are frequently observed to have poor fibrillation resistance. Thus, for useful purposes, it appears the barrier is insurmountable.

In FIGURE 4 is illustrated the presence of the barrier (as described with reference to FIGURE 3) under specific spinning conditions utilizing an aqueous ZnCl2 coagulation bath and an aqueous 60 weight percent ZnClZ spinning solution containing about weight percent of a copolymer of about 92.5 percent acrylonitrile, yabout 6.5 percent methyl acrylate and about 1 percent sulfoethylmethacrylate.

The inability to prepare filments below a certain concentration and under given conditions (i.e., as described herein, a barrier concentration) due to breakage of the filaments in the coagulation bath was apparently encountered by Stanton et al. in U.S. 2,790,700, as evidenced particularly by the data at the top of columns 7 and 8 of the patent. Accordingly, it is believed the presence of this barrier has been significant in the attempts heretofore of being unable to prepare fibers of excellent properties as now provided. The foregoing is not to be construed as imposing any limitation on the operation or scope of the present invention, but is offered merely as an explanation of the problems and difficulties encountered in known methods and a postulation for better understanding of the present invention.

As indicated, acrylonitrile copolymer fibers are prepared in accordance with the invention by spinning into an aqueous saline coagulation bath at conditions inscribed by the area ABCDEF of FIGURE 2. Advantageously and beneficially, the temperature of the coagulation lbath is maintained at between about 25 and 35 C., but the most efficacious temperature employed will depend somewhat on the concentration of the coagulation bath. Thus, salt concentrations in the coagulation bath of from about 25 to 35 weight percent are advantageously employed with bath temperatures of 2535 C. in the present copolymer spinning process. Fibers with particularly outstanding properties are prepared, for example, when spinning into an about 31 to 34 yC. coagulation bath of from about 30 to 35 weight percent of the saline constituent. Y

The temperature of the aqueous saline solution of acrylonitrile copolymer utilized for the spinning of filaments or bers in accordance with the present invention should be between about 55 and 100 C., and preferably between about 65 and 75 C. It is usually experienced that the continuous preparation of filaments cannot be sustained, principally due to filament breakage in the -coagulation bath, when the spinning solution temperature is below about 55 C. Temperatures much in excess of about 100 C. generally lead to solution discoloration resulting in fibers of ofi-color. An additional advantage andv feature of the present method is the increased dye color yields of the spun fibers. This is more fully illustrated by the graph of FIGURE 5 which shows the effect of color yield increase of the spun fibers with increasing spinning solution temperature. About a 10 weight percent solution of a copolymer of about 91.5% acrylonitrile, 7.5% methyl acrylate, and 1% methyl acrylate in anaqueous 60 weight percent vZnClZ solution was spun into an aqueous about 30 weight percent ZnCl2 coagulation bath at about 31.5 C.

The color yield values used in preparing FIGURE 5 were determined by comparing the test sample prepared according to the present teaching and dyed with 0.5 based on fiber dry weight (OWF), Brilliant Green Crystals (Cl. Basic Green 1), with a graded set of dyeings on Orlon 42, an acrylic fiber notably well dyed with basic dyes. A series of 16 dyeings was made on the Orion 42 using from 0.25% to 1.0% Brilliant Green, in steps varying by 0.05% OWF dye. The dyeing procedure followed was to prescour the Orlon 42 fibers for 30 minutes at 70 C. in a 25:1 liquor:fiber bath containing 1% Igepon CO-730 and then rinse well in distilled water. A 25 :l dyebath was prepared at room temperature, containing the desired amount of dye, adjusted to a pH of 4.5-4.9 with sodium acetate. The fiber sample was placed in the dyebath in one pint stainless steel Launder-Ometer containers, sealed with a rubber stopper and placed in the Launder-Ometer. The Launder-Ometer bath was heated from room temperature to the boil in about 20 minutes and held at the boil for 2 hours. The heat -was turned off and the dyeing allowed to run for 30 minutes to cool, and then cooled to at least 100 F. by the slow addition of cold water to the Launder-Ometer. The dyed samples were removed and rinsed well with distilled water and afterscoured with 1% Igepon CO-730 in a 25:1 bath, adjusted to a pH of 3.5-4.0 with phosphoric acid, 4for 20 minutes at C., followed by rinsing well in distilled water and drying at 110 C.

The test sample prepared according to the present teaching was compared with the set of dyeings on Orlon 42. It the test specimen matched the Orlon 42 dyed with 0.5% OWF dye, the color yield was said to be Dyeings lighter or darker than this were given color yield ratings by comparison with the Orlon 42 dyeings, as follows:

The acrylonitrile copolymer compositions that are employed in the present invention are those that `contain between about 85 and 95 weight percent polymerized acrylonitrile. These compositions can be arrived at in any number of possible combinations. Forinstance, acrylonitrile can be copolymerized with one or more other ethylenically unsaturated monomers that are copolymerizable with acrylonitrile, or two such copolymers can be blended, or, a homopolymer of acrylonitirle can be blended with one or more copolymers such that the resulting composition contains between about 85-95 weight percent polymerized acrylonitrile. Advantageously, copolymers, i.e., without blending, are employed. Exemplary of the ethylenically unsaturated monomers that can be copolymerized with acrylonitrile are allyl alcohol, vinyl acetate, acrylamide, methacrylamide, methyl acrylate, vinyl pyridine, ethylene sulfonic acid and its alkali'metal salts, vinyl benzene sulfonic acid and its salts, 2-sulfoethylmethacrylate and its salts, vinyl lactams such as vinyl caprolactam and vinyl pyrrolidone, etc. and mixtures thereof. Copolymers of acrylonitrile and methyl acrylate, -methyl methacrylate, vinyl acetate and the like, and a third monomer of a sulfonated or sulfonic ethylenically unsaturated monomer are advantageously and beneficially employed in the present invention. Copolymers, or more specifically terpolymers, of acrylonitrile, methyl acrylate and 90.6% acrylonitrile, and (2) 9% sulfoethylmethacrylate (SEMA) and 91% acrylonitrile and a polymer of homopolymeric acrylonitrile, the blend containing a total in polymerized form, of about 91.2 percent acrylonitrile,

and 2-sulfoethylmethacrylate (including its salts) are ad- 5 7 percent MA and 1.8 percent SEMA was extruded vantageously prepared following the present teachings. through a G-hole spinnerette into an aqueous zinc chlo- The utile, known aqueous saline solvents for the variride-containing coagulation bath at conditions both within ons fiber forming acrylonitrile polymers that can be emand without the scope of the present invention. The ployed in the present method include zinc chloride, the coagulated filaments were washed, hot stretched 4and various thiocyanates such as calcium and sodium thiocy- 10 dried. The physical properties of the bers were deteronate, lithium bromide, salt mixtures of the so-called mined and divided samples of the fibers were dyed with Lyotropic series, and others recognized by the art as either a dye solution containing 0.5% Brilliant Green has been disclosed, among other places, in the United Crystals (C.I. Basic Green 1) or a dye solution contain- States Letters Paten-ts Nos. 2,140,921, 2,425,192, ing 0.75% Eastman Blue BNN (Cil. Disp. Blue 3). The 2,648,593, 2,648,646, 2,648,648, 2,648,649 and 2,949,435. dyed fibers were subjected to conventional AATCC wash As indicated, the saline constituents that are employed in tests to determine dye bleed, the results of which are the aqueous solvent solutions are present in non-polymerrecorded on a scale of 1 to 5, a number 5 being excellent, dissolving quantities in the coagulation bath, and desirvi.e., none or essentially no dye bleed, and a number 1 ably, the same saline constituents that 4are used in the being poor or excessive dye bleed. The penetration of the solvent solution are also employed in the coagulation 2O dYGSUfnO fh@ ber WHS 3150 determined, 100%1dicatbath. ing through penetration. The results are set forth in After the copolymer filaments are coagulated in the Table I.

TABLE 1 Coag. Dye Penetra- Wash Test Polymer Coag. Bath Hole tion, Percent Bleed Sample Solution Bath Cone. Size Total Denier Tenacity Extension, Yield o. Temp.,C. Temp., Percent (Mils) Stretch (gld.) Percent (gld.)

o. znoiz Brin. Brin Brin. Brin.

Blue Green Blue Green 70.5 31 3 1o 3.4 2.7 33 0.77 75 34 3 Ambient 12. s 43. s 5 12.12 2. s 8. 3 31 0. 85 75 3 3 Ambient 17 43. s 5 9. o7 2. 4 1. 7 48 o. 67 100 10c 2-3 4 7o 12. 5 30. 2 3 9. 2s 5. s 3.1 5e 1. o6 50 100 2 1 70 31. 5 34 3 10 3. 4 2. 6 34 o. 7s 75 100 5 5 coagulation bath following the present invention, they Example 3 are with-drawn from the bath and normally washed essentially completely free of any residual saline constituent. The washed filament, ordinarily in a gel or aquagel condition, is hot stretched to orient the liber to a predetermined extent, frequently about 800 to 1200` percent, in order to impart requisite physical properties. The stretched liber can then ybe given other additional treatments such as crimping, application thereto of various agents such as lubricants and anti-static agent, and subjected to heat treatments or the like either before or after irreversible drying of the gel filament to a characteristically hydrophobic fiber.

The following examples will serve to further illustrate the invention wherein, unless otherwise specified, all parts and percentages are by Weight.

Example 1 A spinning solution of an aqueous about `60 weight percent zinc chloride solution containing about 10 weight percent of a blend of two acrylonitrile copolymers and a homopolymer of acrylonitrile, the polymer solids consisting of, in polymerized form, about 92.5 percent acrylonitrile, `6.5 percent methyl acrylate (MA) and 1 percent ethylene sulfonic acid was extruded at about 701 C. through a multihole spinnerette into an aqueous coagulation bath containing about 34 weight percent zinc chloride at a temperature of about 31.4 C. The coagulated gel filaments were washed essentially completely free of residual zinc chloride, hot stretched about 7X in an aqueous bath, and irreversibly dried to characteristically hydrophobic textile fibers. The thus obtained fibers had a tenacity of 3.2 grams per denier (g./ d.) and an extensibility of 29%. The dyeability lightfastness, resistance to bleed and resistance to fibrillation of the fibers were found to be excellent.

Exam ple 2 A spinning solution as described in Example 1 excepting to contain a blend of tWo copolymers, (1) 9.4% MA The polymer solution of Example 1 was extruded at 69-71 C. into an aqueous zinc chloride coagulation bath under Various conditions, washed, hot stretched about 9.25 and irreversibly dried at C. The so-obtained fibers were generally excellently dyeable to deep shades of coloration with Brilliant Green Crystals (Cl. Basic Green 1) but varying degrees of dye bleed resistance were observed. These results yare set forth in Table II.

TABLE II Coag. Bath Coag. Bath Wash Test Sample No. Temp., C. Conc. Percent Bleed ZnClz Example 4 A spinning solution was spun following the procedure of Example 1 except the polymer dissolved in the solution was, in one case a copolymer of about 91.5% acrylonitrile, 7.5% methyl acrylate and 1% SEMA (designated copolyrner A), and in the other case the copolymer was of about 93.5% acrylonitrile, 5.5% methyl acrylate and 1% SEMA (designated polymer B).

The fibers of copolymer A were found to have excellent fiber properties including resistance to fibrillation and dye fastness properties. In contrast', fibers of copolymers B were inferior in useful fiber physical properties, fibrillation and dye fastness properties and, for most purposes, were unacceptable.

What is claimed is:

1. The method of spinning acrylonitrile polymer fibers comprising spinning an aqueous inorganic saline solution of a polymer of an ethylenically unsaturated monomeric material containing between about 85 and 95 weight percent polymerized acrylonitrile at between about 55 and 100 C. into a coagulation bath of an aqueous inorganic saline solution maintained yat temperatures and saline constituent concentrations within the area bounded by the curve ABCDEF of the attached FIGURE 2.

2. The method of claim 1, wherein said aqueous inorganic saline solution of polymer is an aqueous Zinc chloride solution.

3. The method of claim 1, wherein the same saline constituents are present in said saline solution of polymer and in said saline solution in said coagulation bath.

4. The method of claim 3, wherein said saline constituent is zinc chloride.

5. The method of claim 1, wherein said saline solution of polymer is at a temperature between about 65 and 75 C.

6. The method of claim 1, wherein said` coagulation bath is at a temperature of between about 25 and 35 C.

7. The method of claim 1, wherein said coagulation bath is at a temperature of between about 31 and 34 C.

8. The method of claim 1, where said coagulation bath is at a temperature between about 31 and 34 C. and has a concentration of between about 30 and 35 weight per cent of said saline constituent.

9. The method of claim 1, wherein said polymer consists essentially of, in polymerized form, acrylonitrile, a different ethylenically unsaturated monomer that is copolymerizable with acrylonitrile and a third still different monomer that is `a sulfonated ethylenically unsaturated monomer that is copolymerizable with acrylonitrile.

10. The method of spinning into iibers an aqueous inorganic saline solution at to 100 C. of a polymer of, in polymerized form, between about and 95 weight percent acrylonitrile the remainder being a different ethylenically unsaturated monomer that is copolymerizable with acrylonitrile and a third still different monomer that is a sulfonated ethylenically unsaturated monomer that is copolymerizable with acrylonitrile into an aqueous coagulation bath containing between about 30 and 35 weight percent of the same inorganic saline constituent that is present in said saline solution of polymer at a temperature of between about 31 and 34 C.

11. The method of claim 10, wherein said saline constituent is zinc chloride.

12. The method yof claim 10, wherein said different ethylenically unsaturated monomer is methyl acrylate and said sulfonated monomer is sulfoethyl methacrylate.

13. A fiber prepared by the method of claim 1.

References Cited UNITED STATES PATENTS 2,558,730 9/1951 Cresswell 264-182 2,790,700 4/ 1957 Stanton etal. 264-182 ALEXANDER H. BRODMERKEL, Primary Examiner.

H. H. MINTZ, Alssistant Examiner. 

1. THE METHOD OF SPINNING ACRYLONITRILE POLYMER FIBERS COMPRISING SPINNING AN AQUEOUS INORGANIC SALINE SOLUTION OF A POLYMER OF AN ETHYLENICALLY UNSATURATED MONOMERIC MATERIAL CONTAINING BETWEEN ABOUT 85 AND 95 WEIGHT PERCENT POLYMERIZED ACRYLONITRILE AT BETWEEN ABOUT 55* AND 100*C. INTO A COAGULATION BATH OF AN AQUEOUS INORGANIC SALINE SOLUTION MAINTAINED AT TEMPERATURES AND SALINE CONSTITUENT CONCENTRATIONS WITHIN THE AREA BOUNDED BY THE CURVE ABCDEF OF THE ATTACHED FIGURE
 2. 